The invention concerns an adapter for an exoprosthetic standard part.
Different methods are known for exoprosthetic treatment of a patient who has had a limb amputated.
Thus it is conceivable to work exclusively with exoprosthetic shafts, for example prosthesis shafts, for example in the area of a thigh stump, which are adapted to the size and shapes of the thigh stump. Then in a given case an artificial exoprosthetic knee joint, a calf, as well as a foot, are connected with this prosthesis shaft.
In addition however, there are systems which are anchored with the remaining long bone stump ends so that more natural perceptive faculties, for example in the case of running, can be imparted to the patient. This is known under the name of osteoperception.
For this, for example, an adapter end with a thread is screwed into the remaining long bone, in order to be anchored with the latter. The adapter resembles a pipe piece, which finally emerges out of the tissue on the stump end. Then an exoprosthetic standard part, for example an artificial knee joint, is to be connected to this.
In known adapters of the type described above, the stability of the fixation of the adapter in the long-bone stump is problematic, as is the coupling of a standard part.
An adapter is known from U.S. Pat. No. 3,947,897 that is inserted in the inter-medullary space of the femur, which is provided at its distal end with a coupling device for an exoprosthetic standard part. The seat in the intra-medullary space of the femur should be fixed by application of a bone cement, for example methyl methacrylate. Coupling of the standard part to the distal end should be accomplished by a kind of locking device.
Both the fixing with bone cement and the fixing of the standard part with the locking device are problematic.
Bone cement comes loose after a certain time. Also the locking device does not withstand a permanent seat for the exoprosthetic standard part.
With this background, it is the task of the present invention to provide an adapter for an exoprosthetic standard part that has a favorable long-time fixation behavior and is also permits the standard part to be replaced easily with another one, for example with advanced wear.
This task is solved by an adapter with the characteristics of claim 1.
Accordingly, it is recommended that the adapter be constructed in such a way that it can be inserted into a long-bone stump with a proximal stem part, whereby the stem part is covered, at least partly, by an open-mesh three-dimensional space-network structure and is provided at its other end with a coupling device for an exoprosthetic standard part, where the coupling device consists of a cone and an adapter sheath on it in the conical gluing seat, by which the exoprosthetic standard part is braced.
The open-mesh, three-dimensional space-network structure, which is also called inter-connecting, makes it possible for natural bone material to grow in, through, behind, and around it during the final healing phase, so that the stem part is integrated with the long bone with respect to the substrate flow within a relatively short time and an extremely stable secondary fixation is provided. The growth of bone material into an open-mesh three-dimensional space-network structure is known as such from pure endoprosthetics. We refer here to DE-PS 41 06 971, for example. But a fixation possibility is presented for the first time in the field of exoprosthetic care.
The coupling device provided on the distal side can then be seen freely in connection with the outstanding secondary fixation, because of the said space-network structure. Specifically, the lifetime of the adapter in the long-bone stump is so long, that external wear or breakage phenomena can appear that could no longer provide a precise seat for the exoprosthetic standard part at the coupling site.
The adapter sheath has the advantage of being replaceable, for example if the coupling of a standard part has:led to increased wear or breakage over the course of time. The adapter sheath itself can be replaced as whole.
The seat of the adapter sheath on the cone of the coupling device can also be secured by having a tension screw screwed through the adapter sheath into a threaded hole in the cone.
According to another advantageous variant, the stem part is provided with an surrounding flange for placement on the front edge of the long-bone stump. By this means, the adapter can be placed under stress directly after implantation of the stem part in the long-bone stump, specifically before sufficient bone materials have grown into the open-mesh three-dimensional space-network structure. The flange thus serves to receive the primary load of the forces appearing during the final healing phase and to direct the forces appearing to the cortex of the long-bone stump.
Preferably, the stem part connects, in the direction of the distal coupling device, to an intermediate piece which then runs from the end of the long-bone stump, through the body tissue, until the coupling device lies outside the body. At the site where the intermediate part comes out of the patient""s body, there is then advantageously a sealing part on the intermediate piece. This sealing part protects the break-through site in the limb stump and contributes to the keeping the break-through site easier to keep aseptic. A barrier is thus constructed against severe inflammations that could progress farther into the limb stump.
The adapter described can be further developed advantageously so that the coupling device consists of a cone and an adapter sleeve resting on it in the conical clamping seat, with which sleeve the standard part can be clamped. This adapter sleeve has the advantage of being replaceable, perhaps when the connection of a standard part has led to increased wear or knocked-out pieces in the course of time. The adapter sleeve as such can be replaced as a whole.
The seating of the adapter sleeve on the cone of the coupling device also can be secured additionally by means of screwing a tightening screw through the adapter sleeve into a threaded hole in the cone.
According to an embodiment of the invention, the intermediate piece of the adapter can be adjusted in its length. This has the advantage that only one or a few sizes of the adapter according to the invention need to be manufactured and kept in storage. This reduces the costs significantly.
Alternatively, the intermediate piece consists of a metal mass, whereby stability is increased. Here, however, length adjustments are not possible, so that increased costs must be taken into account.